This latest development is troubling in that many folks still are not staying up-to-date on Microsoft security changes. Botnets turn infected PCs into "zombies" which can be controlled remotely by the bad guys. While the half million potential PCs is a guess, this new botnet is indeed growing very rapidly. Stay safe by always applying ANY security fix promptly.

QUOTE: December 1, 2008 (Computerworld) The worm exploiting a critical Windows bug that Microsoft Corp. patched with an emergency fix in late October is being used to build a new botnet, a security researcher said today. ... it's called "Conficker.a" by Microsoft and is a key component in a new botnet that criminals are creating.

We think 500,000 is a ball park figure," said Macalintal when asked the size of the new botnet. "That's not as large as some, such as [the] Kraken [botnet], or Storm earlier, but it's still starting to grow.

However, the new worm is a global threat, said Macalintal. "This has real potential to do damage," he said. Trend Micro has spotted infected IP addresses on the networks of Internet service providers (ISPs) in the U.S., China, India, the Middle East, Europe and Latin America. The worm first appeared about a week and a half ago, and began spreading in earnest just before Thanksgiving, he added.